I did a test in my application and some features are not working on checkbox, see my log below firebug:

>>> $("#lol");

Object[input#lol] /* Ok, my checkbox */

>>> $("#lol").attr('checked');

undefined

[Checked in browser]

>>> $("#lol").attr('checked');

undefined

>>> $("#lol").attr('checked', 'checked');

Object[input#lol]

>>> $("#lol").removeAttr('checked');

Object[input#lol] /* Works */

>>> $("#lol").attr('checked', '');

Object[input#lol]

>>> $("#lol").attr('checked', null);

Object[input#lol] /* Works */

>>> $("#lol").attr('checked', true);

Object[input#lol]